Oral appliance

ABSTRACT

The oral appliance, either a mouthguard or an orthodontic device, includes a base member having a U-shaped form corresponding to a row of teeth of a user. The base member has inner and outer flanges interconnected by a web which collectively define upper and lower channels within which respectively the upper and lower rows of teeth of the user are received. Upper and lower teeth engaging elements are positioned within the upper and lower channels. The teeth engaging elements are made of EVA which softens at a temperature of 90–95° C. The appliance may also include a tongue tag ( 25 ) and breathing apertures ( 30 ).

This invention relates to an oral appliance.

More specifically this invention relates to an oral appliance which iscapable of being customised to suit the mouth or oral cavity of apatient or user. This invention also relates to a method of making thisappliance using moulding techniques.

This invention finds particular but not exclusive application as a mouthguard for use in sports and as an orthodontic appliance for use incorrecting myofunctional and tooth alignment problems. It will thereforebe convenient to describe the appliance with reference to these exampleapplications. However it is to be clearly understood that the applianceis capable of other applications.

While customised orthodontic appliances are known, these are relativelycostly. This is because each appliance has to be made individually andseparately in a laboratory after a mould or impression of the patient oruser's mouth has been obtained. Naturally it would be advantageous if anappliance could be devised which could be mass produced and which wasalso capable of being adjusted to fit the dimensions of a particularpatient's mouth on the spot while the patient was sitting in a dentalchair.

Similarly, while customised sports mouthguards are the guards of choiceamongst sports people, they are expensive. While mass produced sportsmouthguards are known, they have some real limitations. Specifically,because of a wide range of user mouth sizes and shapes, they often donot fit snugly into the mouth of the user. It would also therefore beadvantageous if an appliance could be devised which was mass producedand which was also capable of being customised to fit snugly into auser's mouth.

The applicant has already developed an oral appliance for repositioningthe temporomandibular joint. Broadly the appliance comprises a baseportion having inner and outer flanges which form respectively upper andlower U-shaped channels for receiving the teeth of upper and lower jawsof a user. The oral appliance is described in detail in the applicant'sprior applications PCT/AU90/00399 and PCT/AU92/00592 which areincorporated directly herein by cross reference. The oral appliancecorrectly positions the temporomandibular joint and positions the lowerjaw downwardly and outwardly. This produces advantageous athleteperformance as well as a more correct orthodontic positioning of thelower jaw relative to the upper jaw. This encourages an improvement inoral habits and can also provide relief for headaches etc. and otherpain conditions.

However, the appliance described above is not capable of beingcustomised to fit a user's mouth. It would therefore be advantageous ifa device which had this ability could be innovated.

According to one aspect of this invention there is provided an oralappliance for placing in the mouth of a user, including:

-   -   a base member having a generally U-shaped form corresponding to        the outline of a jaw of a user, the base member having inner and        outer flanges interconnected by a web which define at least one        of upper and lower channels within which the corresponding rows        of teeth of a user are received; and    -   a continuous layer of thermoplastic material that encompasses        the base member thereby to firmly and securely mount the layer        of thermoplastic material on the base member, the layer of        thermoplastic material forming upper and lower teeth engaging        elements which can be conformed or moulded to suit the        individual teeth of a user by heating to a temperature at which        the layer is plastic and formable.

In one form the base member may define an upper channel within which theupper row of teeth of a user is received. In another form the basemember may define a lower channel within which the lower row of teeth ofa user are received. In a preferred form the base member defines bothupper and lower channels within which respectively the upper and lowerrows of teeth of a user are received.

Preferably, the layer of thermoplastic material is formed of EVA(ethylvinylacetate) which softens at a temperature of 90° C.–95° C. Thelayer of thermoplastic material, e.g. EVA, may have a thickness of 1mm–4 mm, preferably 1 mm–3 mm, e.g. about 2 mm. EVA has a suitable levelof pliability and formability when heated to its softening temperature.

Advantageously, the base member is made of a plastics material which isrigid at temperatures of 90° C.–95° C.

While EVA is preferred for the teeth engaging elements, anythermoplastic having a suitable softening temperature may be used.Preferably the element is malleable at a temperature below 100° C., egso that it can be softened by immersion in boiling water.

Thus the continuous layer also covers a region of the base memberintermediate the upper and lower channels, e.g. the outer walls of theflanges, as well as the channels. The layer encases the base member tofirmly and securely mount teeth engaging elements on the base memberwithout delamination. This overcomes the problem of getting EVA to bondto the base member.

In this specification, the term “engaging” shall bear a broad meaningand shall not be interpreted to mean “retaining” or “latchingengagement”.

Thus the upper and lower teeth engaging elements are capable of beingmoulded to suit the teeth and jaws of a particular user by being heatedabove their softening point, eg by being immersed in boiling water andthen inserted into the mouth of the user. The formable thermoplasticteeth engaging elements can then be conformed to the dimensions andother characteristics of the teeth and jaw of the user. This provides acustomised mouth guard or orthodontic positioning appliance without theneed for time consuming moulds to be taken of a patient's mouth.

The temperature to which the elements must be heated must be reasonablebearing in mind that the appliance is to be placed in the mouth of apatient. It is also important that the thermoplastic does not have anyother toxic or other undesirable properties.

Preferably the continuous layer of thermoplastic material coverssubstantially the entire surface area of the base member and the layeris permanently attached to the base member at the time of manufacture.It is to be understood however that this arrangement is not essentialand that the layer may be continuous without covering the entire surfacearea of the base member.

Preferably, the oral appliance forms a single integral article.

It will be understood that other plastics which are sufficiently strongand rigid and which do not have thermoplastic properties in theappropriate temperature ranges may also be used for the base member.

Thus the base member is reasonably rigid while the teeth engagingelements are softer than the base member.

Optionally the base member may have breathing apertures defined therein,eg centrally positioned, for permitting breathing therethrough. In apreferred form, there are four elongate slot-like apertures defined inthe base member.

Typically the appliance also includes a tongue tag, eg centrallypositioned, defined in the inner flange, for correctly positioning thetongue of a user during use.

In one preferred embodiment, the oral appliance is adapted for use as anorthodontic appliance. In another preferred embodiment, the appliance issuitable for use as a sports mouth guard.

According to another aspect of this invention there is provided a methodof making an oral appliance, the method including the steps of:

-   -   moulding a base member from plastic material in a first moulding        step in a first mould, the member having a generally U-shaped        form corresponding to the outline of the jaw of a user and inner        and outer flanges interconnected by a web which define at least        one of upper and lower channels within which the corresponding        rows of a teeth of a user are received;    -   removing the base member from the first mould and placing it in        a second mould having a larger mould cavity and moulding a        continuous layer of thermoplastic material onto the base member        to form upper and lower teeth engaging elements capable of being        customised to suit the mouth of a user, the layer encasing the        member to thereby firmly and securely mount the layer of        thermoplastic material on the base member.

In one form the base member may define an upper channel within which theupper row of teeth of a user is received. In another form the basemember may define a lower channel within which the lower row of teeth ofa user is received

In a preferred form the base member may define both upper and lowerchannels within which respectively the upper and lower rows of teeth ofa user are received.

Preferably, the base member is injection moulded from polyurethane,polyethylene, polypropylene or santoprine and the layer is injectionmoulded from EVA.

Thus, the oral appliance may be formed in a two step injection mouldingprocess. More specifically, the base member may be injection moulded ina first die or mould and then when it has been formed it is removed fromthe first die and locked into a second die or mould where the layerencasing the member is injection moulded. Thus the teeth engagingelements surround or enclose the base member to effect attachment to thebase member.

Other features of respectively the base member and teeth engagingelements may be as described above with reference to the first aspect ofthe invention.

An oral appliance in accordance with this invention may manifest itselfin a variety of forms. It will be convenient to hereinafter describe indetail two preferred embodiments of the invention with reference to theaccompanying drawings. However it is to be clearly understood that thespecific nature of this description does not supersede the generality ofthe preceding broad description of the invention. In the drawings:

FIG. 1 is a front three dimensional view of an oral appliance inaccordance with one embodiment of the invention;

FIG. 2 is a rear three dimensional view of the oral appliance of FIG. 1;

FIG. 3 is a part sectional side view of the appliance of FIG. 1;

FIG. 4 is a front three dimensional view of the base member of theappliance of FIG. 1; and

FIG. 5 is a rear three dimensional view of the base member of FIG. 4;

FIG. 6 is a front three dimensional view of an appliance in accordancewith a second embodiment of the invention;

FIG. 7 is a rear three dimensional view of the appliance of FIG. 6;

FIG. 8 is a part sectional side view of the appliance of FIG. 6;

FIG. 9 is a front three dimensional view of the base member of theappliance of FIG. 6;

FIG. 10 is a rear three dimensional view of the base member of FIG. 9;and

FIG. 11 is a sectional side view of the base member of FIG. 9.

In FIGS. 1 to 5 reference numeral 1 refers generally to an appliance inaccordance with the invention.

The appliance 1 comprises broadly a base member 2 and two teeth engagingelements 3 and 4.

The base member 2 has a broadly U-shaped configuration sized tocomplement the general U-shape of the jaw of a user when viewed in planview. The base member 2 has a central web 5 and inner and outer flanges6 and 7 projecting both upwardly and downwardly from both the inner andouter edges of the web 5.

The web 5 and flanges 6 and 7 collectively define upper and lowerchannels 10 and 11 within which respectively the upper and lower teethengaging elements 3 and 4 are positioned.

The base member 2 is made of a substantially rigid plastic materialhaving an appropriate mechanical strength. Polypropylyne, polyurethaneand santoprine have been found to be very suitable although otherplastics may also be used. Polyurethane has been used in the illustratedembodiment.

Each of the elements 3, 4 is made of a thermoplastic material which inthe illustrated embodiments is EVA. The EVA softens at 90 to 95° C. andthus can be softened by placing in boiling water.

Each of the tooth engaging elements 3 and 4 also has a broadly U-shapedconfiguration when viewed in plan view. This complements the generalshape of the base member 2. Each element 3, 4 also has a broadlyU-shaped cross sectional configuration with a bottom wall 15 and twoside walls 16 and 17. The shape and width of the channels defined in thebase member 2 and elements 3 and 4 have been specifically designed so asto enable the appliance to accommodate widely varying jaw widths andthereby be capable of being fitted to a large number of patients. Theappliance also includes a notch or cut-out 35 in the upper surface ofthe outer flange 7. The notch 35 has the important function ofpermitting inward or outward adjustment of the arms of the U-shapedmember without causing distortion of the appliance 10. This assists infitting a single size appliance to patients with widely different archsizes.

In the illustrated embodiment, the layer of EVA forming the elements 3,4 extends continuously across the full surface area of the base memberincluding the outer surface of the flanges 6 and 7 and thus covers morethan just the U-shaped channels of the base member 2. The reason forapplying the layer of thermoplastic material across the entire surfacearea of the base member is to mount or attach the EVA layer to the basemember which is made of polyurethane, polypropylene or santoprine. EVAdoes not bond naturally to the base member when it is moulded onto thebase member and thus a way has to be found of securing it to the basemember. This is accomplished by mechanically encasing or enclosing thebase member within the layer of EVA. The inability of EVA to bond to theplastic base member is a major problem to be overcome in manufacturingthese appliances.

The appliance has a tongue tag 25 for positioning the tongue in an exactcentral position. The appliance also has a plurality of holes 30 definedtherein that permit mouth breathing. This is essential for playingsports.

A further feature of the appliance is that the web of the base member 2tapers outwardly from the leading edge thereof up to a point thickeningthe web, and then tapers inwardly after that to the rear endprogressively thinning the web. Thus, the web has a cross sectionalconfiguration so as to substantially occupy the space between the teethof upper and lower jaws of the user. This configuration which is clearlyillustrated in the applicant's prior applications may generally bedescribed as an asymmetrical aerofoil shape having a curved surface onthe lower side. The web may have a thickness of about 6 mm at itsthickest point.

This supports the jaw of a user and encourages the lower jaw to assumeits anatomically correct position relative to the upper jaw. This isbelieved to cause a relaxation of muscles in the head and the neck. Thisconfiguration of the web of the base member opens the “bite” and holdsthe jaw in a more down and forward position. In this position, the jawis more resistant to injury. This jaw position is understood to enhanceathlete performance. Further, the thickening of the web naturally alsostrengthens the appliance.

The appliance 1 is made in a two-step injection moulding process. Thebase member 2 is injection moulded in a first die from polyurethane. Thebase member 2 is then switched to a second die having a larger cavityand the layer of EVA, including the teeth engaging members 3, 4, is thenmoulded onto the base member.

The injection moulding process comprises broadly the injection of aviscous resin from a heated cylinder into the die by means of a plungeror injector. The die is cooled by cooling means, e.g. chilled coolingwater, causing the resin to cure and harden. The moulded article canthen be removed from the die. The injection moulding techniques used toform the appliance would be well known to a person skilled in the artand do not form part of the invention. Therefore, they will not bedescribed in further detail.

In use, the mouth guard may be in one example application be fitted by adentist in a dental surgery. In other applications, the guard may befitted by a user. This is done by heating the appliance up to 90° C. bysoaking it in boiling water. When this occurs the base member remainsrigid while the elements 3, 4 soften making them suitable for beingcustomised to the individual tooth and jaw shape of a user. Theappliance is then placed in position in the mouth of a user and theelements 3, 4 conform to the user's teeth and jaw and then harden inthis position.

In a second embodiment of the invention illustrated in FIGS. 5 to 11,the appliance is used for orthodontic treatment. The orthodonticappliance is the same as that illustrated in FIGS. 1 to 5 with theexception that it does not have breathing holes, e.g. for mouthbreathing, and the base element 2 is thinner, e.g. having an approximatethickness of 2 mm to 4 mm, because it does not have the samerequirements of mechanical strength as the sports guard. The orthodonticappliance is used for myofunctional training and tooth realignment.

Myofunctional training is a clinical procedure which is designed tocorrect bad oral habits, e.g. tongue thrusting, mouth breathing,incorrect swallowing and the like.

In use the appliance is initially fitted by a dentist or orthodontist ina dental surgery. The shape of the elements 3, 4 prior to usecorresponds broadly to an ideal positioning or “bite” of a patientsteeth. To enable the elements 3, 4 to be tailored to a patients specificteeth, the elements 3, 4 arc dipped into boiling water to soften theelements and then inserted into a patients mouth to mould them to thespecific contours of a patient's mouth.

The EVA material from which the elements 3, 4 are formed has a memory sothat it reverts to its original shape when reheated. It reverts partlyto its original shape when heated to 60 to 65° C. and fully to itsoriginal shape when heated above 90° C.

The memory properties of the EVA enable the elements 3, 4 to be used toprogressively correct misalignment of a patients teeth. For example atspaced time intervals, the dentist will typically place the applianceinto water at a temperature of 60–65° C. which causes the elements 3, 4to partly revert to their original shape. The slightly altered shapebrought about by this remoulding causes the appliance to apply pressureto the teeth of a user to correct misalignment. This can be done severaltimes until the patients teeth take up the correct position or the ideal“bite” position.

When the teeth are in the correct position the appliance can be placedinto water at 90–95° C. which causes it to revert fully to its originalposition. The appliance can then be used as a retaining device forretaining the teeth in the correct position and also for carrying outmyofunctional training.

An advantage of the appliance described above is that it enablesindustrially manufactured mouth guards to be customised to a user'smouth very easily and simply, e.g. in a dentist's chair or by a user. Afurther advantage is that the appliance can be applied equally toorthodontic and sports guard applications. A yet further advantage ofthe appliance is that it effectively attaches the EVA elements to thebase member.

The sports mouth guard described above is very effective because itprotects both upper and lower teeth and also the jaw joints. Theorthodontic appliance provides an inexpensive device for correctingmyofunctional and tooth alignment problems.

It will of course be realised that the above has been given only by wayof illustrative example of the invention and that all such modificationsand variations thereto as would be apparent to persons skilled in theart are deemed to fall within the broad scope and ambit of the inventionas is herein set forth.

1. An oral appliance for placing in a mouth of a user, the applianceincluding: a base member having a generally U-shaped form correspondingto the outline of a jaw of a user, the base member having inner andouter flanges interconnected by a web which define at least one of upperand lower channels within which the corresponding rows of teeth of auser are received, said base member being made of a plastics materialwhich is rigid and non-thermoplastic at a temperature of 90° C.–95° C.;and a continuous layer of thermoplastic material that encompasses thebase member thereby to firmly and securely mount the layer ofthermoplastic material on the base member, the layer of thermoplasticmaterial forming teeth engaging elements which can be conformed ormoulded to suit the individual teeth of a user by heating to atemperature at which the layer is plastic and formable.
 2. An oralappliance according to claim 1, wherein the base member defines an upperchannel within which the upper row of teeth of a user is received.
 3. Anoral appliance according to claim 1, wherein the base member definesboth upper and lower channels within which respectively the upper andlower rows of teeth of a user are received.
 4. An oral applianceaccording to claim 1, wherein the layer of thermoplastic material is EVA(ethylvinylacetate) which is plastic at a temperature of 90° C.–95° C.and the base is made out of a polymer from the group consisting ofpolyurethane, polypropylene and santoprine.
 5. An oral applianceaccording to claim 1, wherein the layer of thermoplastic materialforming the teeth engaging elements has a thickness of 1 mm–3 mm andwherein said continuous layer of thermoplastics material substantiallycovers the full surface area of the base member.
 6. An oral applianceaccording to claim 1, wherein a tongue tag is formed on the inner flangeof the base member, the tongue tag being substantially centrallypositioned for correctly positioning the tongue of a user during use andthe base member has breathing apertures defined therein for facilitatingbreathing by a user when wearing the appliance, and a notch defined inan upper surface of the outer flange for permitting inward or outwardadjustment of the U-shaped member.
 7. A method of manufacturing an oralappliance for placing in the mouth of a user, the method including thesteps of: moulding a base member from plastic material in a firstmoulding step in a first mould, the member having a generally U-shapedform corresponding to the outline of the jaw of a user and inner andouter flanges interconnected by a web which define at least one of upperand lower channels within which the corresponding rows of teeth of auser are received, the base member being made of plastics material whichis rigid and non-thermoplastic at a temperature of 90°–95° C.; removingthe base member from the first mould and placing it in a second mouldhaving a larger mould cavity and moulding a continuous layer ofthermoplastic material onto the base member to form upper and lowerteeth engaging elements capable of being customized to suit the mouth ofa user, the layer encasing the member to thereby firmly and securelymount the layer of thermoplastic material on the base member.
 8. Amethod according to claim 7, wherein the base member defines an upperchannel within which the upper row of teeth of a user is received or thebase member defines both upper and lower channels within whichrespectively the upper and lower rows of the teeth of a user arereceived.
 9. A method according to claim 7, wherein the continuous layerof thermoplastic material is moulded substantially fully across thesurface area of the base member in said second moulding step and whereinthe layer of thermoplastic material is injection moulded from EVA whileit is locked in position in the second mould.
 10. A method according toclaim 7, wherein the base member is injection moulded from a polymerfrom the group consisting of polyurethane, polypropylene or santoprine.